Engine starter



Dec. 23, 1924. 1,520,469

B. D. GILSON ENGINE STARTER Filed Deo. 8, 1921 l a 5b Patented Y Dec. 23, 1924. l

1,520,469 PATENT OFFICE.

BERT n. GILsoN, oisrvoHIoAGo, ILLINOIS.

ENGINE STARTER.

Application filed Decembewri, `1921. Serial No. 521,026.

To cll'fwh'z'may concern: Be: it known that n citizen Yof the United iStates, residing at Chicago, in .the county of Cook and State of Illinois, have invented new and useful Improvements in Engine Starters, fof which the following is a specification.v

This invention relates to automatic means for transinittingrotations of a prime mover to a driven member of an engine foLthe purpose o f starting such engine; and it'has primarily in view'the starting of an internal mover, an

combustion engine, pelled vehicles.

In the year such as used in. self pro- 18844 a :British patent issued .to Galloway for an .engine starting device a screw rotatable` 'by a prime a pinion rotatable on the threads l for advance into engagement with a driven member of the engine. The pinion apparently was manually advanced into engagement with said drivenmember, whereupon rotation of a screw transmitted rotations' to the through 4the medium of the pinion, thereby throwing the engine over the dead ycenter and ermitting it to start. Oncestarted it wscomprisin of this screw 4 ound that the driven. member attained much higher speed than the screw (which moreover supposedly would be stopped immediateyA its function was performed) causing the pinion to be thrown out of engagementf with Y the driven member. rious attempts have since been made to cause such pinionto'advance automatically on such screw for the purpose of starting internal combustion engines, the theory on which such atempts were based -being,`that the inertia of' the pinion on the screw, the momentthe latter commenced to revolve, would be sufficient to cause the pinion to start to rotate more slowly, which the pinionwould be compelled to advance axially on the screw into... engagement with the drivenrmemberof the engine. But it has been found that the friction between .the pinion andscrew. is eat enough to overcomeA the inertial retar thepinio-n, and various devices', such as maintaining the pinion unturned during its -advance into engagement with* the driven member of the engine.-

The general object of M this invention isrto provide a structurel 1n which a pinion -is automatically advanceable without resorting said driven member,`

ing tendency f i inencing to function the moment the pinion begins to engage the driven member of the engine and forming aA flexible driving connection between the screw and pinion. The further objects and features of importance of my invention will appear and readily be comprehended lupon perusal of the following description, and by referring to the accompanying drawing, of which:

IFig. l is a side elevation of portions of an internal combustion engine embodying the invention; Fig. 2 shows on a larger scale the portion of the engine supporting the sqtarting device, which latter is shown sub- -stantially. in section through its center; Fig. 3 is a similar-view showing the device in its advanced position land'in the act of rotating the engine flywheel for the purose of starting the engine; Fig. 4 is a view substantially4 in agreement with Fig. 3, but showing the'device again retracted.

The numeral l denotes an internal com-l bustion engine` vand 2 is' theengine crankshaft, to which is rigidly secured a fly wheel 3. On the periphery of this fly Wheel isx placed an annular toothed gear 4, into mesh-with which a pinion 5 is mounted to advance. The pinion is fitted to rotate. on a shaft 6 vof a prime mover 7, -which latter -is preferably an electric motor such as commonly employedfor the purpose of'starting internal`combustion engines. The rear end of the pinion is much enlarged in diameter, and screw-threads 5a are cut into the peripheral surface of this enlarged portion ofl a size to mesh with internal screw threads 8a of a cylindrical housing 8, which latter in turn is rigidly secured to the starting motor-shaft 6, as by a pin 9. It is now noticed that only the rear portion of the pinion lperforation ridesdirectly on the motor shaft. The greater part of this perforation is counter-bored to a larger diameter in order to provide a ber 5b of a size to accommodate a powerful spring l0. The front end .of-the pinion rides on a sleeve 11, which is suitably fastened tothe motor shaft, and this sleeve is made with an enlarged portion lla fitted to rotate in a bearing portion 7a of the motorcasing 7. Or the sleeve may be integral with the shaft bif so desired.

The foregoing description is sufficient to show the operation of the device. When the circuit through the motor is closed, the

cylindrical cham` v motor shaft is forced to rotate, carrying v with" itthe housing 8, .but the pinion 1s free on the shaft, and the slight friction be-"f-` tween the pinion and the shaftv is not suficient to overcome the-inertial which 'tends' to maintain the pinion unturned.' 4Butl a`s`` the pinion threads 5a are in engagementwith the threads' 8a of the revolving housing it'follows that the pinion must advance Ainto mesh the 4fly wheel gear 4. Now it' may .be suggested that the combined frictionjbef,

`tween, pinion and shaft and pinion threads i with the housing threads will suffice to overcome the inertia of the inion,1,but such isV not the case, although it 1s found to besointhe type of drive hereinbefore referred to, in whlch the piniony is made with internal .screw threads riding on screw threads of the y y motor-shaft. There are variousreasons for this apparent, inconsistency, as will be appre- .ciated by those versed in the laws of physics and mechanics. .Without stating -any par-v ticular rule, 'such as may be applied to 'each specific structure, it is sufficient to say that the smallerthe friction surface between the pinion and shaft, the less friction is encountered, and thatvery little' friction surface remainsnin the ystructure ofFig. 2.4 At the same time it will also. be noticed that the pinion iswell supported in'its advanced position, as indicated in Fig. `@so thatthe Ieok turn thefly wheel'.

strengdi needed forpdri'ving purposes is not sacriced when the y secondreason is, that the further the screw-threads are removed from the axisof the shaft, the less the friction load.-A Ithird reason is that, assuming thelsame lead vin all cases, then the lfurther the screw-threads 'are removed from the axis,

ythe easier the angle of the thread helix-hence the less the angular -friction during th'e' axiall advance movement of the .ninion. There is then ya point at which the inertia of the pinionv becomes greater than the friotion 'loadrv That point is reached where the diameter of the screw threads is about four times the diameter of.v the shaft, if the pinion is four times the length of the shaft diameter and is fitted to bear on the shaft,

the full length of the pinion. But as the pinion, in thev structure of my invention, only hassuHiCient'bearing on the'- shaft ,toA support lts own weight, in its retarded position, it is found that the dia-meter of the screw threads need only be about twicethe eration', in other wordsthatit floats.

inion is advanced to vthe forcereduired *to lcompress the spring l becomes greater than'the reslstance of the flywheel, whereupon the latter commences to turn, tl1er'eby', relieving the pressure on the spring, lwhich commences to expand and to pushthe -ini'on lback orto speed up the fly-wheel. I ynow one or more 'cylinders are 'on "the 'compression stroke itis found that rapidly, causing the pinion to move forward -an'd possibly entirely to compress-the spring. When' the vcylinder com ression ystrokel is completed there is a sud en drop in the resistance resulting in a lrepulsionof the pinion' and alsp'eedf acceleration ofthe flywheel.. Thus itis seen that power is stored ythe resistance ofthe iiy-'wheel willincrease in the spring while the'liy-wheel resistance increases, 'and' that l this stored power is utilized to `accelerate collapses. Furthermorethat the pinion is in a constant state of. axial movement vduring the "starting'lelpe advantage of the floatin pinion is that' the wear on the'pinion and y-wheel'gear is dis- I tributed'over the entire surface of theseparts, lwhereas in' the starting devices now in use thewear lalways occursin the same place,l thereby shortening" the life of the .i

parts. Thel springlO should occupy nearly the entire-space Within'the pinion, leaving 4only,sufficient"freedom forthe pinion to `move forwardto touch'the iy-wheel before the compression ofthe spring commences.

It happens occasionally that vibrations of i the runmng engine cause the pinion to advance until,v it touches Ythe flyfwheel `whichth'en instantly throws the pinion back.

Gear,

This `isnot of.any`.great` consequence, ex-

cept that it subjects the parts to undue wear, and also that the'V noise of 'such icollision is objectionable.-It is vdesired to introduce means tending tomaintain the pinion .re-

tracted, when not in use, and such means Inav take the shape of a slight drop '11b of the peripheral front endl surface' of the sleeve*v Yin 11. Such drop must, of course, be ,ex-"1" tremely slight vand gentle', in order not to exaggerated4 in the Fig. 2 of the drawing in lorder to make the'drawing `more readily readable. Or it may vconsist in the intro-- duction cfa very sensitive spring v 12 urging form` a positive -obstruction to lthe desired l advance of lthe pinion, and .it has been much Us the pinion into retracted position, and l'yet f -not strong enough to interfere with 'the defsired vad'vanoemove'ment when the motor is started. This sprin is indicated in'r Fig.,3,

and it is shown Afu y'compresised. `When 1t expands, and the pinion., isgfully retracted."

it ,occupies the entire length .ofthe space within-.the pinion. f

I claim:

l. In an enginestar'ter, an engine driven-- member, ametor driven shaft, an internally threaded housing on the shaft, apinion .bearing on the shaft and normally Within said.

housing,v said pinion having a threaded enlargement engaging the housing threads'foi' projecting the pinion axially. on the shaft out of the housing and into`engagement with Said engine driven member, aresinlientl)Y compressble member within said pinion and opposing the advance of the pinion after reaching said engine driven member, and means for yieldingly maintaining the pinion iny retracted position.

2. In an engine starter, a driven member of the engine, an electric motor, a rod at` of said rod, a member normally Within said housing and interconnected therewith to be axially advanced, thereby on the rod, when the rod and housing commence to rotate, into engagement With said driven member, and means within said enclosed member yieldingly opposing further advance of the-enclosed member.

In testimony whereof I have hereunto affixed my signature.

BERT D. GILSON. 

